1. Field of the Invention
The present invention relates to a head module for discharging liquid by driving energy-generating elements included in head chips via a wiring board, a liquid discharge head including a plurality of the head modules, and a liquid discharge apparatus including a plurality of the head modules. More particularly, the present invention relates to a technique for greatly reducing a space used for establishing connection to the wiring board.
2. Description of the Related Art
A line-head inkjet printer is an example of a liquid discharge apparatus in which nozzles for discharging ink (liquid) are arranged over a length corresponding to the width of a recording sheet. Such an inkjet printer includes a line head (liquid discharge head) having heating resistors (energy-generating elements) for discharging ink. The heating resistors are arranged so as to face the respective nozzles and are driven to discharge the ink from the nozzles.
The line-head inkjet printer is capable of printing an image having a width corresponding to the width of the recording sheet using the line head. Unlike a serial inkjet printer, which prints an image by moving a serial head (liquid discharge head) along the width of a recording sheet, a mechanism for the movement along the width direction of the recording sheet is not included in the line-head inkjet printer. Therefore, the line-head inkjet printer is advantageous in that vibration and noise can be reduced and the printing speed can be greatly increased.
The line head includes two head-chip lines in each of which relatively small head chips having heating resistors arranged therein are arranged in a certain direction. The head chips included in the two head-chip lines are arranged in a staggered pattern so that the overall length of the head chips corresponds to the width of the recording sheet. An example of such a line head is disclosed in Japanese Patent No. 3405757 (hereinafter called Patent Document 1).
According to Patent Document 1, the entire body of the line head is manufactured as a single product. Therefore, if a portion of the line head is defective due to, for example, a defect in a certain head chip, the entire line head is determined to be defective. Therefore, quality management of the line head is difficult and mass productivity thereof is low. If a portion of the line head malfunctions, the entire body of the line head is replaced by another line head and high repair costs are incurred.
To overcome the above-described disadvantages, a line head obtained by combining a plurality of head modules together has been developed. Each head module includes head chips that are arranged to form head-chip lines over a length corresponding to a fraction of the width of the recording sheet. Each of the head chips in the head-chip lines has electrodes connected to wires provided on a wiring board. The head modules are combined together to from a line head having a length corresponding to the width of the recording sheet. An example of such a line head is disclosed in Japanese Unexamined Patent Application Publication No. 2005-138528 (hereinafter called Patent Document 2).
The module-type line head is expected to reduce the fraction defective and increase the mass productivity because production and quality management can be carried out in units of head modules. In addition, service efficiency can be improved because the defective head modules can be individually replaced by other head modules. In addition, line heads can be provided in various sizes by changing the number and combination of the head modules. Accordingly, the line heads can be efficiently designed and manufactured.